So your main account with your 70 is linked to your new RAF account? Won't work the way you want it to.

Having a 70 linked to a lowbie kills the bonus.

A 70 boosting you will drop your xp per kill, which is then tripled for any lowbies in the group that are linked to each other and not to the 70.

For your purposes if you've already established the link? make a lowbie on your veteran account, group it with the new lowbie, get a friend or guildie to boost you with an unlinked 70.

Filling the remainder of the group with other lowbies will improve the xp per kill slightly.

I have a 70 main on my unlinked account. I had a friend invite me, which started my A account linked to him, then created a chain of 3 more accounts linked A>B>C>D, so I can boost the 4 of them with my main.